Engine blocks (cylinder blocks) may include one or more cylinder bores that house pistons of an internal combustion engine. Engine blocks may be cast, for example, from cast iron or aluminum. Aluminum is lighter than cast iron, and may be chosen in order to reduce the weight of a vehicle and improve fuel economy. Aluminum engine blocks may include a liner, such as a cast iron liner. If liner-less, the aluminum engine block may include a coating on the bore surface. Cast iron liners generally increase the weight of the block and may result in mismatched thermal properties between the aluminum block and the cast iron liners. Liner-less blocks may receive a coating (e.g., a plasma coated bore process) to reduce wear and/or friction.
The inner surface of each cylinder bore is machined prior to coating so that the surface is suitable for use in automotive applications with suitable wear resistance and strength. The machining process may include roughening the inner surface, applying a metallic coating to the roughened surface, honing the metallic coating to obtain a finished inner surface, and cleaning the inner surface to remove burrs and debris.